Field
The inventive concepts described herein relate to a delta-sigma modulator, and more particularly, relate to a delta-sigma modulator capable of noise-shaping and an audio codec having the same.
Description of Related Art
Delta-sigma modulators are commonly employed in a high-resolution data converter through quantization noise suppression using a noise-shaping characteristic of quantization noise and an oversampling method.
An analog delta-sigma modulator used in a high-resolution analog-to-digital converter may be classified into a discrete-time method using a switched-capacitor integrator according to a configuration method of a loop filter and a continuous-time method using an active filter including resistors and capacitors.
The delta-sigma modulator may adapt an active filter as a loop filter. The delta-sigma modulator may minimize quantization noise necessarily generated in a step for converting an analog signal into a digital signal. Moreover, the delta-sigma modulator may be widely used as an analog-to-digital converter. The delta-sigma modulator is classified into a discrete-time delta-sigma modulator and a continuous-time delta sigma modulator according to a type of a loop filter.
The discrete-time delta-sigma modulator has the characteristic that the variation of a filter coefficient is relatively small and the expendability of a frequency is enhanced, using a switched-capacitor circuit. The discrete-time delta-sigma modulator also has other characteristic that power consumption is large, a switching noise occurs in an input terminal, and an anti-aliasing filter is additionally used for minimizing an aliasing generated when a high-resolution signal is changed into a low-resolution signal.
On the other hand, the continuous-time delta sigma modulator provides a unique anti-aliasing function, and has a characteristic that a filter characteristic is changed based on the variation of a passive component according to a process variation, a temperature, and the like.